Totem-pole gate driver VS Active pull down VS Fast Fet turn off

[6666]

With regards to fast coil fet turn off in a PI,
Just wondering if any body has done any bench top testing and comparison of a totem-pole gate driver verses single transistor active pull down of the gate and which one is fastest to turn off the fet ? Thanks.

[qute1]

i only know that i batch test mosfets to find the lowest rdson resistance as a sharper turnoff will always help and even with ten seemingly identical mosfets one or two will be 0.2 ohms lower than the rest and always seem to give better depth in pi's as less ring down time in the coil is provided.

[Xtrem]

Here are my camparisions

minipulse (MPP) original driver


MPP totem pole mod


and last the driver from Lorenz Pulse 5 (very good driver)

[waltr]

Here are my camparisions

minipulse (MPP) original driver
[ATTACH]43170[/ATTACH]

MPP totem pole mod
[ATTACH]43171[/ATTACH]

and last the driver from Lorenz Pulse 5 (very good driver)
[ATTACH]43172[/ATTACH]

Yes, the Lorenz looks best but does it use a SAME MOSFET as the MMP?
If not then more likely the faster Turn-off is a function of the MOSFET and not the gate driver.

Please list Which MOSFET in Lorenz verse MMP.

[dbanner]

Here are my camparisions

minipulse (MPP) original driver
[ATTACH]43170[/ATTACH]

MPP totem pole mod
[ATTACH]43171[/ATTACH]

and last the driver from Lorenz Pulse 5 (very good driver)
[ATTACH]43172[/ATTACH]

Could you do a comparison with totem pole driver of TDI proto pro. I will post the schematic.

[dbanner]

Please take note of the orientation of the pnp transistor, I think it is drawn incorrectly.

[waltr]

Please take note of the orientation of the pnp transistor, I think it is drawn incorrectly.

Yes, there are many errors in that schematic. Also notice op-amps (U1, U3) with feed-back R into non-inverting input!!!

[Xtrem]

Yes, the Lorenz looks best but does it use a SAME MOSFET as the MMP?
If not then more likely the faster Turn-off is a function of the MOSFET and not the gate driver.

Please list Which MOSFET in Lorenz verse MMP.

These are real bench tests, mosfet for Lorenz i have use are IRFP450(in the shematic IRFP460) , for MPP IRF740.
turn-off is in this situation is a function of the driver , because IRFP450 has 2600p gate capacity, IFR740 has 1400p,
lower capacity - faster (easier)turn-off

[Xtrem]

Theoretical only, i think the driver of TDI is maybe a litle faster as my driver(totem mpp), because of the 1n(C parallel to
10K(R3 ???)
there are incorrections in the schematic.

[waltr]

These are real bench tests, mosfet for Lorenz i have use are IRFP450(in the shematic IRFP460) , for MPP IRF740.
turn-off is in this situation is a function of the driver , because IRFP450 has 2600p gate capacity, IFR740 has 1400p,
lower capacity - faster (easier)turn-off

Ok,
IRF740- total Gate charge = 63nC
IRFP450- total gate charge = 150nC
So the Gate drive circuit makes a big difference.

Now to see the gate drive circuit of the Lorenz.

[dbanner]

Here is a very good document for mosfet driver circuits explaining a lot of the technical stuff. The lorenz circuit appears to be just a pnp turnoff circuit with anti parallel diode on the gate drive.
there is a good discussion on bipolar totem driver circuits in the document.

[6666]

Here is a very good document for mosfet driver circuits explaining a lot of the technical stuff. The lorenz circuit appears to be just a pnp turnoff circuit with anti parallel diode on the gate drive.
there is a good discussion on bipolar totem driver circuits in the document.

Thanks for the PDF,

[Mark-VA]

Would it be possible to increase the ground balance pot from 100k to 150k give a more expanded (finer adjustments) GB setting?

[Elliot]

Please take note of the orientation of the pnp transistor, I think it is drawn incorrectly.

Does anyone have a correct schematic for the TDI Pro?

[Mr.Jaick]

Here is a very good document for mosfet driver circuits explaining a lot of the technical stuff. The lorenz circuit appears to be just a pnp turnoff circuit with anti parallel diode on the gate drive.
there is a good discussion on bipolar totem driver circuits in the document.

I reed the document but still have question about three components
here is a pic of the drive


1_ the 470nF caps parallel with the 15k resistors
does it help with the ton/toff time of the BJTs and if, how?
and it's 1nF in TDI schematic what's the difference ?

2_ the anti-parallel diode
which apparently protects the base-emitter junction of Q3 against reverse breakdown at the beginning of the turnonprocedure but why a 2.2V Zener ?

3_ R10 the 100k parallel with Gate and source
is it for some sort of protection or stops turn off ringing without compromising the actual turn off time ?